Recently, an intelligent drug delivery system, which can reduce a side effect caused by drug abuse and maximize drug effect by allowing drug to have selective effect on a specific area, is drawing attention.
As an example of such an intelligent drug delivery system, various methods of using a stimuli-sensitive material to external stimulus such as pH and temperature have been proposed, and various stimuli-sensitive materials are disclosed in the related art references (Y. H. Bae, in Controlled Drug Delivery: Challenges and Strategies, K. Park, ed., Am. Chem. Soc., Washington, D.C., 1997, Chap. 8, 147-162 page).
Among these materials, polyelectrolyte obtained by a polymerization of vinyl monomer having poly (N-isopropyl acryl amide) sensitive to temperature, and carboxyl, sulfone, amine, or ammonium sensitive to pH has been used as a material for intelligent drug delivery (“Polyelectrolyte Gels; Properties, Preparation, and Applications”, R. S. Harland and R. K. Prud'homme, eds., ACS Symp. Series #480, Am. Chem. Soc. Washington, D.C., 1992, Chap. 17, page 285). A co-polymer grafted with temperature-sensitive and ph-sensitive enzymes is known as a dual sensitive intelligent polymer material.
A limitation in preparing such a related art material for intelligent drug delivery is that it is difficult to regulate the molecular weight and components of the material to control the drug delivery effect. In order to solve the limitation, U.S. Pat. No. 6,784,266 discloses a method of preparing a dual sensitive smart hydrogel by preparing sulfon amide vinyl monomer sensitive to pH and synthesizing a poly (N-isopropyl acryl amide), which is a material sensitive to temperature, using the atom transfer radical polymerization.
Besides, in order to minimize a side effect and maximize a drug delivery effect, various attempts have been globally conducted to develop a new stimuli-sensitive drug delivery material.